1. Field of the Invention
This invention relates to ink jet printing processes for making images, and particularly, color images. More particularly, this invention relates to ink jet printing processes and the elements used therein for the production and protection of large size, full color images.
2. Description of Related Art
The use of ink jet printing processes in the manufacture of multicolor images is well known in the art. In such processes, ink droplets are emitted from a nozzle and deposited on substrates, such as paper, to form an image. In order to obtain good quality images, rapid absorption of the ink into the substrate is required, but at the same time the ink colorant must be retained at or near the surface of the substrate with lateral ink migration limited to the resolution of the printer. Ink jet printing and its use in making full color images is reviewed in general by Werner E. Haas in "Non-Impact Printing Technologies": Chapter 13, pages 379-384, of IMAGING PROCESSES AND MATERIALS--NEBLETTE'S EIGHTH EDITION, Edited by John Sturge, Vivian Walworth & Allan Shepp, (1989) Van Nostrand Reinhold, New York. In this review, Haas reviews the methods of ink jet printing and briefly addresses criteria needed in inks and papers.
To achieve high quality images in ink jet printing, the substrate, e.g., paper, is coated with a formulation to meet the requirements discussed supra. Although paper stock is extensively used as the substrate for ink jet printing, many other materials are used including plastic films and sheets, fabrics, metals, woods, glass, and the like. When transparencies are to be produced, typically a coated transparent plastic film or sheet is used as the substrate. Since aqueous based inks are the common type of ink used in ink jet printing processes, substrate coating formulations typically are hydrophilic and contain appropriate absorptive materials. Such coated substrates may be illustrated by Patterson et al., U.S. Pat. No. 4,732,786; Desjarlais, U.S. Pat. No. 4,775,594; Light, U.S. Pat. No. 5,126,195; and Kruse, U.S. Pat. No. 5,198,306. Patterson et al. disclose coated paper and film as ink jet printing substrates in which the coating comprises a pigment, a binder, an insolubilized hydrophilic polymer and a polymer of a polyvalent cation. Desjarlais discloses an ink jet transparency with wetting properties which result in even surface distribution of ink on the transparency. The transparency comprises a transparent resinous support and a clear coating thereon containing a water soluble resin, a water insoluble resin, a fluorosurfactant, and non-volatile organic acid including glycolic, methoxy acetic, dibasic carboxylic, or tribasic carboxylic acid. Light discloses transparent image-recording elements that contain ink-receptive layers that can be imaged by liquid ink dots. The ink receptive layers contain a vinyl pyrrolidone, particles of a polyester, a polymeric alkylene oxide, a polyvinyl alcohol, nonylphenoxypolyglycidol and inert particles. Kruse discloses a recording transparency and its method of preparation from water solution. The transparency disclosed comprises a transparent substrate and a coating of a synthetic transparent cellulosic polymer and a surfactant composition comprising nonionic detergent, anionic detergent and complexing agent.
A method of preparing a color printed record using hot-melt ink jet technology is disclosed by Helinski, U.S. Pat. No. 4,666,757. A printed record in color is disclosed which comprises a transparent sheet on which is jet-printed subtractive color hot-melt inks. The inked surface of the transparent sheet is adhered to the surface of an opaque backing sheet, usually white in color. The transparent sheet is identified as a transparent flexible material such as a plastic film material marketed under the trademark Mylar. The opaque backing sheet is identified as a sheet of plain white uncoated paper. It is further disclosed that the two sheets may be held together by suitable affixing means such as a transparent adhesive coating preapplied to the surface of the opaque sheet.
An image protective film is disclosed by Yoshida, U.S. Pat. No. 5,217,773. An image protective film and its method of use is disclosed in which the film comprises a base layer, a release-layer formed of a resin having no compatibility with the base layer and an adhesive layer formed of a thermoadhesive resin. The film is superposed on an image surface of an object article such that the adhesive layer comes in contact with the image surface and thereafter heated. The base layer is separated from the object article and the adhesive layer and the release layer remain on the object article to form a protective layer. A variety of images are disclosed including those formed by ink jet recording systems.
Current ink jet printing processes, inks and substrates are capable of producing high quality four color images in sizes ranging from office copy up to sizes useful for posters, displays and billboards. However, application of ink jet printing has been limited largely to such uses as office copy and the like where environmental and abrasion damage to the finished ink image is unlikely. When used as posters, displays and particularly billboards, the water sensitive ink jet image and underlying substrate must be protected from rain, sunlight, and other environmental contaminants and should likewise be protected from abrasion and graffiti to provide adequate useful life to the image displayed. Although advances have been made in providing protection for color ink jet images on substrates which are flat or planar, there is an industry need for a method for applying protected, distortion-free, ink jet images to objects having non-planar topography. There also continues to be an industry need for a simplified process to provide protected, distortion-free, full-color ink jet images, particularly, for use on large format posters, billboards and the like.